The objectives of this proposal are the design, synthesis and evaluation of specific inhibitors of human placental aromatase (estrogen synthetase). These inhibitors include enzyme-generated irreversible inhibitors and also competitive reversible inhibitors. Specific inhibitors of human placental aromatase should be valuable tools in studying estrogen biosynthesis in placental tissue and in other tissues. They may also be of value in the study and treatment of estrogen-dependent tumors, and in studying the role played by peripheral aromatization of androgen in male endocrinology. Mechanistic studies with these inhibitors should also be of interest in further examination of the mechanism of action of aromatase.